Encoder

Abstract

Disclosed is an encoder including a rotary member and a fixed member. The fixed member is provided with an electrode having A-channel, B-channel and C-channel patterns, the rotary member is provided with contacts which are to be opposed to the electrode. A-C state switches from OFF to ON at each rotation of the rotary member for one click angle from a stable click position in both CW and CCW direction. During CW rotation for one click angle, B-C state remains unchanged from OFF; during CCW rotation for one click angle, B-C state switches twice between ON and OFF.

1. An encoder comprising:
 a fixed member; 
 a rotary member; and 
 a click mechanism for stabilizing the rotary member at each rotation for a predetermined click angle, one of the fixed member and the rotary member being provided with an electrode having A-channel, B-channel and C-channel patterns, the other of the fixed member and the rotary member being provided with contacts which are to be opposed to the electrode so that as the rotary member is rotated, a state between the A-channel and the C-channel and a state between the B-channel and the C-channel switch between a first state and a second state according to contact/noncontact between the respective contacts and the electrode, wherein 
 one of the first state and the second state is a conductive state, and the other of the first state and the second state is a nonconductive state, wherein 
 (a) the state between the A-channel and the C-channel switches between the first state and the second state at each rotation of the rotary member for the click angle, 
 (b) as the rotary member is rotated for the click angle in one direction from a reference phase where the state between the A-channel and the C-channel is in the first state while the rotary member is stabilized by the click mechanism, the state between the B-channel and the C-channel remains unchanged from the first or second state, and 
 (c) as the rotary member is rotated for the click angle in an opposite direction from the reference phase, the state between the B-channel and the C-channel switches twice between the first state and the second state. 
 
   
   
     2. An encoder according to  claim 1 , wherein the state between the B-channel and the C-channel switches such that one of the first state and the second state continues longer than the click angle and the other of the first state and the second state continues shorter than the click angle. 
   
   
     3. An encoder according to  claim 1 , wherein when the rotary member is stabilized by the click mechanism, at least one of the A-channel pattern and the B-channel pattern of the electrode is electrically disconnected from the contacts. 
   
   
     4. An encoder according to  claim 1 , wherein the A-channel pattern, the B-channel pattern and the C-channel pattern (the three patterns) of the electrode are separated from each other, and the contacts include sliders which are electrically connected together and are opposed to the A-channel pattern, the B-channel pattern and the C-channel pattern, respectively, wherein as the rotary member is rotated, the individual sliders are permitted to slide on the three patterns in turn. 
   
   
     5. An encoder according to  claim 4 , wherein the A-channel pattern, the B-channel pattern and the C-channel pattern are spaced apart from each other in a rotating direction of the rotary member. 
   
   
     6. An encoder according to  claim 1 , wherein a duty ratio of the first/second state between the A-channel and the C-channel is 50%. 
   
   
     7. An encoder according to  claim 1 , wherein count up and count down are carried out in a detection circuit when the state between the A-channel and the C-channel switches between the first state and the second state.